摘要:
This invention describes the composition and method of preparation of heteroflocculated packet emulsion clusters containing a light sensitive and selectively photosensitized silver halide emulsion particles and particles of photographic agents such as dye-forming coupler particles. The silver halide emulsion particles are associated with a layer of adsorbed peptizing gelatin with an isoelectric pH of P.sub.1 and the grafted gelatin of the gelatin-grafted-polymer particles comprising the photographic agent has an isoelectric pH of P.sub.2 such that P.sub.1 is different than P.sub.2. At least one of the peptizing and grafted gelatins is an isoing gelatin which is sufficiently derivatized to remove ionic groups thereof such that approaching the isoelectric pH in an aqueous solution of the isoing gelatin causes massive heteroflocculation. Formation of packet emulsion clusters is achieved by heteroflocculation between oppositely charged silver halide particles and gelatin-grafted-latex polymer particles comprising the photographic agents by shift of the pH to within 0.5 pH units of the isoelectric pH of the isoing gelatin and at a value between the two isoelectric pH values of two different types of gelatins used. The heteroflocculated packet emulsions can be further stabilized via hardening of the gelatins surrounding the particles in the packet clusters using a concentrated gelatin hardener. Such packet emulsion clusters are suitable for use in mixed packet color photography.
摘要:
The invention describes silver halide packet emulsion grains or crystals that are conventionally precipitated using gelatin of a given isoelectric pH, surrounded by a layer of gelatin-grafted-polymer particles wherein the grafted gelatin has a different isoelectric pH and the said gelatin-grafted-polymer particles are optionally chemically bonded to the gelatin surrounding the silver halide microcrystals. Such packet emulsions can form the basis for a mixed-packet color photographic system.
摘要:
A method of preparing a monosize silver halide emulsion of which most of the silver halide crystals are of the twinned octahedral type is provided. An aqueous solution of a silver salt and an aqueous solution of an alkali metal or ammonium halide in an aqueous dispersing medium containing a protective colloid are mixed at such concentration that the silver halide is nucleated, causing the silver halide nuclei to increase in size in the presence of a silver halide solvent by Ostwald ripening to produce a population of twinned octahedral seed crystals. Then the maximum rate of addition of silver salt and alkali metal or ammonium halide which is possible without renucleation occurring and the minimum rate of addition of silver salt and alkali metal or ammonium halide which is possible without Ostwald ripening occurring is determined and the seed crystals are caused to grow by adding to the aqueous dispersing medium aqueous silver salt solution and aqueous alkali metal or ammonium halide solution at a rate between the predetermined maximum and minimum rates and then at intervals the maximum and minimum addition rates are re-determined and the addition rates of silver and halide are adjusted to ensure that at all times during the crystal growth stage neither renucleation nor Ostwald ripening occurs, the p Br of the liquid phase being maintained above 0.15 during the whole crystal growth stage. The silver halide emulsions are useful for preparing photographic material.